An antiporter (also called exchanger or counter-transporter) is a cotransporter and integral membrane protein involved in secondary active transport of two or more different molecules or ions across a

phospholipid membrane The lipid bilayer (or phospholipid bilayer) is a thin polar membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around all cells. The cell membranes of almost all organisms and many vir ...

such as the

plasma membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (t ...

in opposite directions, one into the cell and one out of the cell. Na⁺/H⁺ antiporters have been reviewed. In secondary active transport, one species of solute moves along its electrochemical gradient, allowing a different species to move against its own electrochemical gradient. This movement is in contrast to

primary active transport In cellular biology, ''active transport'' is the movement of molecules or ions across a cell membrane from a region of lower concentration to a region of higher concentration—against the concentration gradient. Active transport requires cellul ...

, in which all solutes are moved against their

concentration gradient Molecular diffusion, often simply called diffusion, is the thermal motion of all (liquid or gas) particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size (mass) of ...

s, fueled by

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. Transport may involve one or more of each type of solute. For example, the Na⁺/Ca²⁺ exchanger, found in the plasma membrane of many cells, moves three sodium ions in one direction, and one calcium ion in the other.

Role in Homeostatic Mechanisms

Na+/H+ Antiporters Antiporters, such as Na+/H+ antiporter protein, allows ions H+ and Na+ to travel across a membrane in order to change a concentration gradient. When pH within a cell is higher or lower than the optimal range it can be detrimental, therefore, the Na+/H+ antiporter detects the pH level out of range and is activated to transport ions as a homeostatic mechanism to bring the pH level back to optimal range. There are differences among the types of Na+/H+ antiporter families present in

eukaryotes Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...

and prokaryotes. Prokaryotic organisms contain antiporter families such as NhaA, NhaB, NhaC, NhaD, NhaP, along with NapA. The most prominent functions, including pH regulation, are completed by Na+/H+ antiporter family NhaA in prokaryotes like Escherichia coli. Plants are sensitive to high amounts of salt, which can halt certain necessary functions of the eukaryotic organism, including photosynthesis. For the organisms to maintain homeostasis and carry out crucial functions, Na+/H+ antiporters are used to rid the cytoplasm of excess sodium by pumping Na+ out of the cell. These antiporters can also close their channel to stop sodium from entering the cell, along with allowing excess sodium within the cell to enter into a vacuole.

References

External links

* * Integral membrane proteins Transport phenomena {{membrane-protein-stub

Role in Homeostatic Mechanisms

See also

References

External links